1. Technical Field of the Invention
The present invention relates to a stator for a rotary electric machine which is used as a motor or a generator in a vehicle, for example, and relates to a method of manufacturing the stator.
2. Related Art
Various stators for rotary electric machines have been known, which are used in vehicles. One of these known stators includes a stator comprising an annular stator core that has a plurality of slots in the circumferential direction, and a stator winding formed of wire members that are wound about the stator core with a plurality of portions of the wire members being stacked and disposed in the respective slots. A rotary electric machine provided with such a stator has suffered from a rasping and peculiar noise or magnetic noise ascribed to the vibration of the stator core, which vibration is induced by the vibration of the stator winding during the operation of the rotary electric machine. To take measures against such a problem of peculiar noise or magnetic noise, several suggestions have been made.
For example, patent document JP-A-H03-270657 discloses that a thermoplastic resin is impregnated in an insulating sheet interposed between the peripheral wall surface of each slot of a stator core and the wire members accommodated in the slot. The patent document further discloses that only the portions of the wire members located inside the insulating sheet are connected to each other by the thermoplastic resin that has been heated and melted, while these portions are also connected to the insulating sheet.
Patent document JP-A-H04-208040 discloses that an insulating sheet made of a vibration-damping insulating material is interposed between the peripheral wall surface of each slot and the wire members in the slot to attenuate the vibration of the wire members in the slot.
However, regarding the technique disclosed in the patent document JP-A-H03-270657, the thermoplastic resin is required to have a very high expansion coefficient in order to have the thermoplastic resin fully distributed between the portions of the wire members each having a circular cross section and adjacently located in each slot. In addition, since the positions of each of the portions of the wire members are difficult to control, the wire members are likely to come into contact with the stator core, causing insulation failure.
Regarding the technique disclosed in the patent document JP-A-H04-208040, the insulating sheet made of the vibration-damping insulating material is required to have a certain thickness in order to obtain a satisfactory attenuation effect by the insulating sheet, leading to lowering of the space factor. The term “space factor” refers to a proportion of an area occupied by wire members in a cross section of a slot. The space factor is obtained using a formula; (Total cross section of wire members disposed in a slot)/(Cross section of the slot).